This invention relates generally to refrigeration, and more specifically to refrigeration methods and apparatus for simultaneously satisfying heating and cooling demands.
Refrigeration apparatus or machines are frequently employed to cool a fluid such as water which is circulated through various rooms or enclosures of a building to cool these areas. Often, the refrigerant of such machines rejects a relatively large amount of heat at the condenser of the machine. This rejected heat is commonly dissipated to the atmosphere, either directly or via a cooling fluid that circulates between the condenser and a cooling tower. Over a period of time, the rejected heat represents a substantial loss of energy, and much attention has been recently directed to reclaiming or recovering this heat to satisfy a heating load or demand.
One general approach to reclaiming this heat is to employ a booster compressor to draw and further compress a portion of the refrigerant vapor passing through the condenser of the refrigeration machine. This further compressed vapor is then passed through a separate, heat reclaiming condenser. A heat transfer fluid is circulated through the heat reclaiming condenser in heat transfer relation with the refrigerant passing therethrough. Heat is transferred from the refrigerant to the heat transfer fluid, heating the fluid and condensing the refrigerant. The heated heat transfer fluid may then be used to satisfy a present heating load or the fluid may be stored for later use, and the condensed refrigerant is returned to the refrigeration circuit for further use therein.
With refrigeration machines having both a refrigeration, or cooling, circuit and a heating circuit has described above, it is desirable to vary the capacities of the heating and cooling circuits to meet changing heating and cooling loads, and typically this is done by varying the refrigerant flow rates through the circuits. Difficulties may arise, though, when the refrigerant flow rate through the heating circuit is very low. More particularly, under such conditions, the booster compressor may significantly raise the temperature of the refrigerant vapor passing therethrough, and the refrigerant may approach temperature levels which cause the refrigerant to chemically breakdown. Such a chemical breakdown of the refrigerant may produce acidic compounds which can damage the structure of the refrigeration machine. Preventing excessive vapor temperature in the heating circuit is complicated by a number of facts. First, it is preferred to vary the capacities of the heating and cooling circuits substantially independent of each other. Thus, the capacity of the cooling circuit may be anywhere between its minimum and maximum values when excessive vapor temperatures are approached in the heating circuit. Second, with certain refrigeration machines of the general type described above, the specific manner for preventing excessive vapor temperatures in the heating circuit will vary in accordance with the actual capacity of the cooling circuit when these excessive temperatures are approached.